Australia: Baby dugongs' return to Great Barrier Reef suggests vital seagrass recovering from Cyclone Yasi

Robert Baird and Nathalie Fernbach ABC North Qld 22 May 17;

An increase in the number of baby dugongs on the Great Barrier Reef suggests seagrass ecosystems are recovering well after recent flood and cyclone events.

A James Cook University report on the distribution and abundance of dugongs and turtles on the southern Great Barrier Reef, between Hinchinbrook Island and southern Queensland, showed the number of dugong calves had gone from zero per cent after Cyclone Yasi in 2011 to ten per cent of the visible population in late 2016.

The Great Barrier Reef Marine Park Authority's (GBRMPA) Roger Beeden said the fact that dugongs are reproducing suggests their ecosystem is in better health.

"Because they have obviously found enough seagrass to sustain them and not only to sustain their growth but also to be able to reproduce," Dr Beeden said.

Mammal easier to count than blades of grass

Seagrass is the primary food source for dugongs and sea turtles, and seagrass beds are used by many fish and marine species as a nursery.

It can be tricky to assess the health of seagrass habitats as inshore beds can be hard to access, but Dr Beeden said dugongs are easy to spot in aerial surveys and give an indication of seagrass health.

"They are a really useful supplement to what happens with programs looking at seagrass numbers themselves," Dr Beeden said.

It has been shown that seagrass meadows can recover well from cyclone damage but Dr Beeden said there were concerns after Cyclone Yasi and subsequent floods escalated the impacts of repeated damage.

"For example in Cleveland Bay, which is just offshore from Townsville, the magnitude of the effect of those cyclones was very substantial — not just on the standing crop of seagrass but also on the seeds of the seagrass which were in the sand," Dr Beeden said.

"So we were very concerned about what the return time and health of those seagrass systems was going to be."

Dugongs' conservation status is vulnerable and it is believed that most of the world's dugong population lives in Australian waters.

The JCU dugong survey was conducted as part of a report for the GBRMPA on the distribution of dugongs and marine turtles in Moreton Bay, Hervey Bay and the southern Great Barrier Reef.

It estimated there were 5,500 dugongs on the southern Great Barrier Reef in late 2016.


Dugong calves make strong comeback on reef
ELISE DONALDSON Australian Associated Press 22 May 17;

Dugong calf numbers, wiped out on the Great Barrier Reef six years ago, have recovered and are thriving, new research has found.

An aerial survey conducted late last year has shown a significant recovery of the large sea mammal's population since Cyclone Yasi and widespread flooding damaged their seagrass food supply in 2011.

Numbers in the southern region of the reef have increased to more than 10 per cent of the current population, according to the James Cook University survey.

Scientists estimated there were some 5500 dugongs in the waters between Hinchinbrook Island and the Queensland-NSW border at the time of the survey, with just over half found in the reef's world heritage area.

JCU Professor Helene Marsh said the results were positive news for what was a "globally significant" dugong population on the Great Barrier Reef.

"Dugongs play an important ecological role in coastal marine ecosystems and the status of dugong populations in an area can be used as an indicator of general ecosystem health," Prof Marsh said.

The survey is part of an integrated monitoring and reporting program which assesses the progress of the Australian and Queensland government's Reef 2050 Plan.

Program director Dr Roger Beeden said the surveys would be completed every five years and were vital to conservation management of the reef.

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